In response to the clear need for a comprehensive, organized approach to large-scale collection and analysis of structured, longitudinal clinical data for patients with the fragile X syndrome (FXS), the Institute for Basic Research (IBR), the Fragile X Clinical and Research Consortium (FXCRC), partnered with Columbia University and the National Fragile X Foundation (NFXF), have developed a plan for systematic data collection, management and analysis to be achieved during a four-year funding period that is anticipated to begin in the fall of 2011. The proposed plan builds on a collaborative, research-oriented infrastructure that has been built with funding from a previous CDC contract that is now in its third and final year. During this period, the scientific and administrative leadership recruited 21 clinics into the FXCRC, created a leadership and committee infrastructure, and used this infrastructure to design the content and structure of an extensive Registry and Clinical Database system. This system was then implemented as a secure web-based application, allowing participating clinics, with IRB approval, to obtain consent from patients and their families to gather information on structured paper forms that could be entered into the on-line Registry and Clinical Database. Achievement of the plan described in this proposal will significantly increase the number of well- characterized individuals with FXS as well as add important new domains of longitudinal clinical and public health data that can be used to address important research questions regarding this vulnerable population.